Extremely bird-like wings to boot (7)
I believe the answer is:
besides
'to boot' is the definition.
(I've seen this in another clue)
'extremely bird-like wings' is the wordplay.
I cannot really see how this works, but
'wings' could be 'sides' (I've seen this in another clue) and 'sides' is present in the answer.
The remaining letters 'be' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for besides that I've seen before include "Moreover" , "to boot" , "also is available" , "See bids (anag)" , "In addition, as well" .)